The present invention relates to apparatus for producing a continuous tobacco stream. Such apparatus may constitute distributors in cigarette rod making machines or in machines for the making of wrapped tobacco filler rods which are severed at regular intervals to yield plain cigarillos or cigars.
German Pat. No. 480,335 discloses a tobacco stream forming apparatus wherein a conveyor draws tobacco from a magazine and the thus withdrawn tobacco is fed into a duct which accumulates an intermediate supply of tobacco particles. The duct is followed by a device which compacts the particles of the intermediate supply and delivers compacted tobacco to a passage wherein the particles advance into the range of a conveyor for transfer of tobacco particles into the stream forming zone. The compacting device utilizes a wheel with retractible needles which draw tobacco particles from the duct and introduce the particles into the aforementioned passage. The wheel is mounted opposite a stationary wall of the compacting device. The purpose of the wheel is to insure uniform densification of tobacco which leaves the duct. To this end, the wheel is driven by an adjustable friction clutch. The means for delivering tobacco particles from the passage to the transfer conveyor comprises a carded drum and a picker roller which expels the particles from the carding. The picker roller breaks the particles of tobacco and produces large quantities of tobacco dust.
It has been found that the just described conventional apparatus cannot insure uniform compacting of tobacco particles between the duct and the passage. The German patent discloses that the wheel of the compacting device rotates at an irregular rate in that its speed decreases when a row of needles delivers a batch of tobacco particles into the passage because the batch encounters the mass of condensed tobacco particles in the passage. The driving element of the friction clutch then rotates relative to but continues to engage the driven element in order to insure that the freshly transferred batch is compacted to the same extent as the tobacco which is already received in the passage. The needles are thereupon retracted whereby the compacting action upon the freshly transferred batch decreases and the friction clutch is capable of increasing the rotational speed of the wheel. The just described mode of operation of the compacting device brings about alternating densification and expansion of tobacco in the passage whereby the variations in density of tobacco which advances in the passage entail irregular delivery of tobacco into the range of the carded drum. The fluctuations of density of tobacco in the passage between the compacting device and the carded drum are caused in part by retractible needles and in part by the periphery of the wheel because such periphery engages the adjacent particles and its speed varies for the aforedescribed reasons. Friction between the particles of tobacco and the stationary wall of the compacting device is not constant, and this also contributes to unpredictability of compacting action upon tobacco which is transported from the duct into the passage upstream of the carded drum. As a rule, friction between tobacco and a stationary wall will depend on the nature of tobacco as well as on the moisture content of tobacco particles.
The factors which influence densification of tobacco particles in the patented apparatus are so unpredictable that such apparatus failed to gain acceptance in the tobacco processing industry.